awful.menu: Move code from rc.lua to awful.menu

Fixes: #2524

awesomerc.lua

@@ -85,21 +85,6 @@ awful.layout.layouts = {
 }
 -- }}}
 
--- {{{ Helper functions
-local function client_menu_toggle_fn()
-    local instance = nil
-
-    return function ()
-        if instance and instance.wibox.visible then
-            instance:hide()
-            instance = nil
-        else
-            instance = awful.menu.clients({ theme = { width = 250 } })
-        end
-    end
-end
--- }}}
-
 -- {{{ Menu
 -- @DOC_MENU@
 -- Create a launcher widget and a main menu
@@ -162,7 +147,9 @@ local tasklist_buttons = gears.table.join(
                                                   )
                                               end
                                           end),
-                     awful.button({ }, 3, client_menu_toggle_fn()),
+                     awful.button({ }, 3, function()
+                                              awful.menu.client_list({ theme = { width = 250 } })
+                                          end),
                      awful.button({ }, 4, function ()
                                               awful.client.focus.byidx(1)
                                           end),

lib/awful/menu.lua

@@ -541,6 +541,28 @@ function menu.clients(args, item_args, filter)
     return m
 end
 
+local clients_menu = nil
+
+--- Use menu.clients to build and open the client menu if it isn't already open.
+-- Close the client menu if it is already open.
+-- See `awful.menu.clients` for more information.
+-- @tparam[opt] table args Menu table, see `new()` for more information.
+-- @tparam[opt] table item_args Table that will be merged into each item, see
+--   `new()` for more information.
+-- @tparam[opt] func filter A function taking a client as an argument and
+--   returning `true` or `false` to indicate whether the client should be
+--   included in the menu.
+-- @return The menu.
+function menu.client_list(args, item_args, filter)
+    if clients_menu and clients_menu.wibox.visible then
+        clients_menu:hide()
+        clients_menu = nil
+    else
+        clients_menu = menu.clients(args, item_args, filter)
+    end
+    return clients_menu
+end
+
 --------------------------------------------------------------------------------
 
 --- Default awful.menu.entry constructor